Concrete Pavement Joint Design and Construction

Louisiana Transportation Conference

February 10, 2009

Dr. Michael AyersDirector of Education and

Training

Why Joint Concrete Pavements?

Control natural cracking caused by internal slab stresses.

Stresses from:Shrinkage from cement hydrationTemperature gradient (curling)Moisture loss (drying shrinkage/warping)Restraint to contraction (subbase friction/bond)

Why Joint Concrete Pavements?

Control natural transverse & longitudinal cracking from internal slab stresses.

40-80 ft 15-20 ft

Types of Joints

Joint types:ContractionConstructionIsolation (and, if necessary, expansion)

Each can occur in either the transverse or longitudinal directions.Also specialty joints (e.g., transitions, terminal joints in continuously reinforced, etc.).

Types of Joints

Transverse Contraction:

Types of Joints

Longitudinal Contraction:

Types of Joints

Transverse Construction:

Types of Joints

Longitudinal Construction:

Types of Joints

Isolation:

Formula for Maximum Joint Spacing

ML = T x CsML = Maximum length between joints (in.)T = Slab thickness (in.)Cs = Support constant

Use 24 for subgrades or unstabilized [granular] subbases;Use 21 for stabilized subbases (ATB, CTB, lean concrete) or existing concrete or asphalt pavement;Use 12 to 15 for thin bonded overlays on asphalt

0%

10%

20%

30%

40%

50%

60%

70%

80%

0 10 20 30 40 50Traffic, million ESALs

Perc

ent s

lab

crac

king

20 ft

18 ft

17 ft

15 ft

Effects of Joint Spacing

Joint Spacing Recommendations

For Streets, Roads, and Highways:Use ML = T x Cs

Keep ratio of transverse to longitudinal spacing at less than 1.5Keep maximum spacing of transverse joints to 15 ft for plain concrete unless local history shows longer panels work (e.g., low CTE aggregate)

Examples of Locations

TB019P

Examples of Locations

IS006P

Examples of Locations

EB237P

Adjust to Meet Utilities!

Proper Boxouts

If You DO Box Out Properly…

If You DON’T Box Out Properly…

TIMING & DEPTHConcrete Pavement Joint Construction

Crack Control Window

Time

Con

cret

e S

treng

th

Too Late:Cracking

SawingWindow

Too Early:Raveling

Internal Stress EqualsConcrete Strength

Minimum Strength to AvertExcessive Saw Cut Raveling

Inte

rnal

Stre

ss

IMPORTANCE OF CURING!

Levels of Raveling

Unacceptable:

Moderate:

None:

www.hiperpav.com

How to Test the Window…

ASTM C Now = “Alright, Start To Make Cut Now”

Not Just Timing…DEPTH!

Joint Depth Recommendations

TransverseT/4 on unstabilizedT/3 on stabilized

LongitudinalT/3

Timing is a factor

TRANSVERSE

LONGITUDINAL

T/4

T/3

T/3

T/3

CONSTRUCTIONConcrete Pavement Joint Construction

Embedded Steel – Pre-Placed

Embedded Steel – Inserter Placed

Location Identification

Joint Formation/Sawing

Common Types of Pavement Saws

Walk-Behind►

Span Saw ▼ Early Entry▼

Proper Location, Time & Depth = Joint Activated Over Dowel Bars

Dowel Drilling

TROUBLESHOOTINGConcrete Pavement Joint Construction

STEEL OPTIMIZATIONConcrete Pavement Joint Construction

WHY?

Dowel Bars:Never “designed”; typically selected based on thickness – what if pavement always fails by fatigue and not erosion?Proven dowel bar retrofit uses 50% of the steel of standards.“Non-standard” specs drive up costs.

Tie Bars:Again, never “designed” but requirements must change based on subgrade/subbase, climate, etc.Subgrade drag theory does not adequately define relationships.

Research focusing on optimizing and “greening” design!

Emerging Dowel Geometries

Potential for Steel Savings

Dimensions (in.)

Spacing (in.)

Dowels per 15 ft Joint

Total Steelper

Joint (in3)

Steel Reduction

per Joint

Round 1¼ x 18 12 15 330 -Square 1¼ x 18 14 13 365 -10%

Rectangle ¾ x 2½ x 12 18 10 225 32%

Diamond ¾ x 4½ x 4½ 20 9 135 59%

Tapered ¾ x 1.67 to 3.33 x 12 18 10 150 55%

Strategic placement of steel at the joint + Potential for greater dowel spacing =

Less steel per joint

Table after ACI 360R-06 and 302.1R-04.

DowelCAD 2.0

FREE software that predicts pavement behaviors based on different round and elliptical dowel bar spacings and configurations.Results can help designers significantly decrease embedded steel content (and costs) without compromising performance!Program based on finite element analyses.

Tiebar Research

Research report is almost completed. Will provide a practical design: Design considers subbase type, number of lanes/shoulders, concrete material properties, climate (location and placement time), concrete thickness, steel yield, etc.

References

The following sources were used in the development of this Webinar:- IS006P, Intersection Joint Layout- IS061P, Design and Construction of Joints for Concrete Streets- EB237P, Concrete Pavement Field Reference: Prepaving- TB019P, Concrete Intersections – A Guide to Design and Construction- TB010P, Design and Construction of Joints for Concrete Highways- TB012P, Joint and Crack Sealing and Repair for Concrete Pavements- TB016P, Early Age Cracking of Concrete Pavements: Causes and Repairs

Visit the ACPA Bookstore at www.pavement.com

FHWA References

Some great pertinant (and FREE) FHWA resources available here http://www.fhwa.dot.gov/pavement/pub_listing.cfm?areas=Concrete:- FHWA-IF-03-003, Pavement Preservation Checklist #06 Joint Sealing Portland Cement Concrete Pavements- FHWA-IF-02-052, High Performance Concrete Pavements: Alternative Dowel Bars for Load Transfer in Jointed Concrete- FHWA-RD-98-172, Joint Sawing Guideline: The Window of Opportunity

… and don’t forget HIPERPAV here http://www.hiperpav.com/!

Thank You!!!

Please contact Michael Ayers or Robert Rodden with questions or comments:

mayers@pavement.comrrodden@pavement.com